The effectiveness of Selective Photothermolysis (SD) is well established. SP theory, when applied to the treatment of vascular lesions, in particular Port Wine Stain birthmarks, calls for a laser emitting 5 J/cm2 at 577 nm, with pulse duration of 3 msec. But, lasers meeting the important pulse duration requirement are unavailable. Flashlamp excited dye lasers produce pulses at most 0.5 msec long, and CW type lasers with robotic attachment produce pulses 30 msec in duration or longer. Data does not exist in the important 1 to 10 msec regime. Clinical end points for the overly short pulses are unsatisfactory, leading to purpura and repeated treatments, while, with the overly long pulses, selectivity is lost resulting in epidermal damage. Phase I determined that a single FEDL cannot produce the requisite pulse duration, but a solution for the problem was recommended. Subsequent to the Phase I studies, a laser built according to the recommendation was used in tests on animals. These tests show that optimum pulse durations are decidedly better. An ultra long pulse dye laser for commercial use will be built in Phase II and tested clinically. New protocols at reduced fluences will eliminate acute purpura and reduce the number of treatments necessary for clearing. This will allow the treatment of leg veins, a heretofore intractable problem. PROPOSED COMMERCIAL APPLICATION: There is a large market for dermatology treatments off the type described in this project. New laser technology that would make the laser treatment better, more widely applicable, more efficient, and less expensive would have a significant on the commercial aspects of this field.